Referring to FIG. 1, a conventional microtitre tray includes a two-dimensional array of wells arranged in one common plane when viewed from its top. Liquid biological samples are placed in some or all of the wells and analyzed. For instance, biological samples, e.g., for DNA sequencing, are often placed and transported in microtitre trays. In addition, reagents can be added to the samples in the wells and/or other treatments such as heating, cooling, centrifuging, filtering, diluting can be performed on the samples in the wells. Subsequently, in many cases the samples are taken directly from a microtitre tray and inserted into an analysis system, e.g., a DNA sequencer, for further detailed clinical analysis.
During the above described processes, the samples in the wells can spill or leak out from the wells. In some instances, the leaked out samples can flow into other wells. This causes loss of valuable samples, cross contamination thereof and renders the samples useless for any clinical analysis. Further, even if there is only a negligible probability of the cross contamination, when the results of the clinical analysis are to be presented to a peer review or a lay person review, i.e., a jury or a tribunal, the process of reducing the chance of cross contamination may become relevant evidence in interpreting the results of the clinical analysis.
In order to avoid the cross contamination problem, conventional microtitre trays are provided with closed lids that tightly fit over each of the wells. The lids may reduce the chance of the cross contamination and the loss of samples to nil. However, this solution, hinders the use of automated analysis systems by requiring the use of cumbersome robotic arms to remove the lids.
An automated system utilizes the uniform characteristics of microtitre trays, e.g., the location and sizes of well openings. In other words, introduction of samples into microtitre wells can be achieved by a two-dimensional array of syringes arranged to match with the locations of the well openings. Further, a two-dimensional array of probes can be inserted into the wells of a microtitre tray for clinical analysis of the sample simultaneously. Other examples of automated analysis systems include micropipeting work station, which is a robotic station, that would perform all of the sample transfer and other processes automatically.
In the above described exemplary automated systems, the closed lids require an additional step of removing the lids. If this lid removal step is to be automatically performed, then an additional mechanism to remove the lids and to test whether or not all the lids have been removed would be required. This makes automated analysis systems more cumbersome and expensive.
In one alternative embodiment, loose-fitting lids are provided to lessen the force required to remove the lids by the automated analysis systems. The loose lids, however, introduce additional risks, such as unwanted removal during sample transport, and the need to ensure the lid was properly replaced after the sample was accessed.
As another alternative, an aluminum foil or an adhesive backed aluminum foil can be used to cover the opening of the wells. In this alternative, the foil is peeled away or pierced through by syringes or probes that need to access the wells. Another alternative is to use septum-based sample lids. Similar to the foil, the septum-based lid is pierced by the syringes or probes to access the wells. All of those embodiments require additional hardware to automate. For instance they require feedback systems to ensure that the piercing or removing the foil is in fact achieved.
In some automated analysis systems, only fragile or flexible probes can be utilized. These probes would not be sufficiently rigid to penetrate or pierce through the foils or the septum-based lids discussed above. An example of these types of probes is used in an automated capillary electrophoresis system described in U.S. Pat. No. 5,885,430 which is incorporated herein by reference. Another example of fragile and flexible probes are small fiberoptic tips utilized for analysis of samples using absorption or emission techniques.
Therefore, it would be desirable to provide a lid mechanism to microtitre trays that can prevent cross contamination of samples and, simultaneously, can accommodate the fragile and flexible probes described above.